1. Field of the Invention
This invention relates to a semiconductor device and a manufacturing method thereof and is applied to a multilayer wiring using an air gap structure, for example.
2. Description of the Related Art
Conventionally, a multilayer wiring using an air gap structure is proposed (for example, refer to Jpn. Pat. Appln. KOKAI Publication No. H9-237831). The air gap structure is a structure in which a material used to isolate adjacent wirings from each other is not a solid material represented by a silicon oxide film but a gaseous material such as air.
A conventional general manufacturing method of a multilayer wiring using the air gap structure is as follows.
First, a wiring structure is temporarily formed in an insulating film. At this time, it is general to use a carbon film or resist as a material of the insulating film. Further, it is general to form a barrier film for prevention of diffusion by use of a metal material such as Ta (tantalum) or TaN (tantalum nitride) before forming a wiring layer containing metal such as Cu (copper) or Al (aluminum) as a main component.
Then, a porous film is formed on the above wiring structure.
Next, air gaps are formed by etching portions of the insulating film between wiring layers through the porous film by using O2 as etching gas.
However, since an oxide gas such as O2 is used in the above etching process, the barrier film tends to be oxidized and corroded and the wiring also tends to be oxidized and corroded. This is because the barrier film and wiring are formed of a metal material, exhibit almost no oxidation resistance and are easily oxidized and corroded by an oxidation gas such as O2. Particularly, when the wiring structure is formed by using Cu as a main component, the above tendency becomes significant since the Cu itself does not have oxidation resistance.